At the base of the Golden Gate Bridge, a small sign basically begs for a high-five.

Beneath the southern end of the Golden Gate Bridge is the “Gibraltar of the West Coast,” a fort built to protect the San Francisco Bay from naval attack.

There is no trying to fall in love with this Star Wars fountain, you just do or do not.

The last remaining relic of San Francisco's glittering 1915 Panama Pacific Exposition.

A huge musical instrument played by the ocean.

Once the fastest ship from San Francisco to Tahiti, the Galilee now lays in pieces in three different cities.

The first AIDS memorial chapel in San Francisco and one of only a few in the U.S.

A speck of nature and art in one of San Francisco’s most notorious neighborhoods.

Created in 1972, the famous sculptor's intricately detailed monument to San Francisco is overflowing with city landmarks.

Early prototype for Frank Lloyd Wright's Guggenheim.

The second building of its name to occupy this location might be the finest flatiron building in San Francisco.

San Francisco's oldest surviving monument and meeting place for 1906 survivors.

This concrete tangle of square pipes has stood as a proud thorn in the city's side since the '70s.

Gold Rush ship-turned-hotel buried underneath San Francisco's financial district.

Not merely a museum – but a whirring powerhouse that offers a subterranean peek into the heart and soul of cable car operations.

Nine centuries-old fortresses guard the walls of this medieval Romanian city.

This hauntingly beautiful cemetery outside a medieval citadel is full of winding paths and ivy-covered graves.

This once-derelict building is now one of the most beautiful bookstores in the world.

This museum offers a journey back to the Belle Epoque era of Romania.

This historic black and white monastery is one of Bulgaria's architectural jewels.

In this historic region, homes and churches are carved into ancient volcanic rock formations.

While not Turkey's deepest underground city, this subterranean redoubt is the largest.

Natural rock formation, or biblical artifact that saved Earth's wildlife two by two?

Standing proud atop a Turkish bluff, this Ottoman palace has retained its grandeur despite being abandoned for centuries.